Mounting mat with lower friction surface for assembling and higher friction surface for mounting

ABSTRACT

A mounting mat ( 16 ) comprising at least one inorganic layer ( 18 ) comprising inorganic materials suitable for mounting a pollution control element in a pollution control device. A friction—inducing material ( 20 ) is disposed on at least one side of the inorganic layer ( 18 ). The deposited friction—inducing material ( 20 ) defines a higher friction area exhibiting a static coefficient of friction higher than that of the inorganic materials. A lower friction layer ( 20 ) is disposed so as to cover at least a portion of the higher friction area and define an exposed surface area of the mounting mat ( 16 ). The exposed surface area exhibits a lower static coefficient of friction than that of the higher friction area. The lower friction layer ( 20 ) no longer covers a substantial portion of the higher friction area, after the mounting mat ( 16 ) mounts a pollution control element ( 14 ) in a pollution control device ( 10 ).

The present invention relates to pollution control devices, inparticular to materials used to mount a pollution control element in thehousing of a pollution control element, and more particularly, to a matthat has at least one lower friction surface for assembling and at leastone higher friction surface for mounting a pollution control element inthe housing of a pollution control element.

BACKGROUND

There are different types of devices used to control the level ofpolluting gases exiting from the exhaust of an internal combustionengine. Such pollution control devices include catalytic converter,diesel particulate and other engine exhaust filters or traps, as well asdevices that combine both catalytic and filtering or trapping functions.Various techniques for assembling such pollution control devices areknown. Each of these techniques include mounting (i.e., canning) apollution control element (e.g., a catalytic element, exhaust filter,etc.) within a housing , by positioning the pollution control elementinside of the housing and disposing a mounting material, typically inmat or sheet form, in the gap between the pollution control element andthe housing. The sheet-shaped mounting mats are wrapped around theexterior of the pollution control element. Mounting materials have alsobeen molded into a cylindrical or tubular shaped mounting mat andslipped over the pollution control element, or insert molded around thepollution control element (e.g., a monolithic catalytic element). Afterthe mounting mat is disposed around the pollution control element, theresulting assembly is canned. Conventional canning techniques includethe use of mechanical stuffing (e.g., using a stuffing cone),tourniquet, and clamshell canning operations that result in the mountingmat being disposed within the gap between the can or housing andpollution control element.

The mounting material is required to apply sufficient mounting pressureto prevent movement of the pollution control element within the housingduring the operation of the pollution control device. At the same time,pollution control elements are typically relatively fragile. Therefore,the pressure exerted by the mounting material must be kept low enough toprevent the pollution control element from being crushed. In addition,the gap between the housing and the pollution control element can changesignificantly during the operation of the pollution control device. Thisgap can also vary somewhat as the result of the differences inmanufacturing tolerances and material choices between the pollutioncontrol element and the housing. As a result, the mounting material alsoneeds to be resilient enough to maintain an acceptable level of mountingpressure as this gap changes.

There is a continuing need for improving such mounting techniques andfor mounting materials that not only exhibit the mounting propertiesdesired, but also facilitate the mounting of a pollution control elementinside a corresponding pollution control device housing. The presentinvention provides a new mounting mat and technique for mounting apollution control element in a housing of a pollution control device.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a mounting matis provided that comprises (a) at least one inorganic layer (e.g., inthe form of a web, sheet or mat) comprising inorganic materials suitablefor mounting a pollution control element in a housing of a pollutioncontrol device, with the at least one inorganic layer having oppositesides and each side defining a major surface area; (b) afriction-inducing material disposed on at least a portion of the majorsurface area, of at least one of the sides of the at least one inorganiclayer, so as to define a higher friction area exhibiting a staticcoefficient of friction higher than that of the inorganic materials; and(c) a lower friction layer disposed so as to cover at least a portion ofthe higher friction area and define an exposed surface area of themounting mat, with the exposed surface area exhibiting a lower staticcoefficient of friction than that of the higher friction area. The lowerfriction layer is operatively adapted so as to no longer cover asubstantial portion of the higher friction area, after the mounting mathas been used to mount a pollution control element in a housing of apollution control device.

It can be desirable for the mounting mat to further comprise an optionalbonding layer disposed so as to adhere the friction-inducing material onat least the portion of the major surface area of at least one of thesides of the at least one inorganic layer. The bonding layer may atleast partially adhere at least part of the lower friction layer to theat least one inorganic layer so as to cover at least a portion of thehigher friction area.

In another aspect of the present invention, a pollution control deviceis provided that comprises a housing; a pollution control elementmounted in the housing; and a mounting mat according to the presentinvention. The mounting mat is disposed between the pollution controlelement and the housing.

In an additional aspect of the present invention, a method is providedfor making a mounting mat. The method comprises:

-   -   (a) providing at least one inorganic layer comprising inorganic        materials suitable for mounting a pollution control element in a        housing of a pollution control device, with the at least one        inorganic layer having opposite sides, and each of the opposite        sides defining a major surface area;    -   (b) disposing a friction-inducing material on at least a portion        of the major surface area, of at least one of the sides of the        at least one inorganic layer, so as to define a higher friction        area exhibiting a static coefficient of friction higher than        that of the inorganic materials; and    -   (c) disposing a lower friction layer so as to cover a portion of        the higher friction area and define an exposed surface area of        the mounting mat, with the exposed surface area exhibiting a        lower static coefficient of friction than that of the higher        friction area,    -   wherein the lower friction layer is operatively adapted so as to        no longer cover a substantial portion of the higher friction        area, after the mounting mat has been used to mount a pollution        control element in a housing of a pollution control device.

It can be desirable for the method to further comprise disposing anoptional bonding layer so as to adhere the friction-inducing material onat least the portion of the major surface area of at least one of thesides of the at least one inorganic layer. The bonding layer may beapplied so as to at least partially adhere at least part of the lowerfriction layer to the at least one inorganic layer.

The lower friction layer facilitates the canning of the pollutioncontrol element with the mounting mat and can also reduce the amount ofwear experienced by the tools (e.g., a stuffing cone) used in canning(e.g., stuffing) a pollution control element into a housing with aconventional friction inducing mounting mat like those mounting matsdisclosed in US Patent Application Publication Nos. 2008/0175764 and2009/0025377, which are incorporated herein by reference in theirentirety. Therefore, it can be beneficial to perform a conventionalmechanical type (e.g., stuffing, tourniquet and clamshell) canningtechnique using the present invention. For example, by lowering theinitial coefficient of friction of one or both major surfaces of themounting mat, the mat can be less likely damaged during the canningprocess.

Such damage may include one or a combination of mat rolling, shearing inthe plane of the mat, tearing of the mat, or breakage of the fibers,which can reduce the durability and performance of the mounting mat.When the coefficient of friction is too high between the mat and thehousing during a stuffing operation, the mat can slip and becomedisplaced from its desired position on the pollution control element.Canning with mounting mats having too high of a coefficient of frictioncan also cause scuffing, tearing, cracking, and bunching of the mat,which can result in localized areas of the mounting mat having higher orlower than desired mat mounting densities, or pinching of the mountingmat (e.g., as the housing is tightened around the pollution controlelement during a tourniquet or clamshell process).

In addition, when canning a pollution control element (e.g., a ceramicelement) using a mounting mat having friction-inducing material (e.g.,abrasive material) on one or both of its major surfaces, the housing orthe pollution control element or both may be damaged during the canningprocess. In particular, for example, the friction-inducing material canscratch or gouge the surface(s) of the housing and/or pollution controlelement brought in contact with the corresponding surface of themounting mat during the canning process. Such scratching and/or gougingmay accelerate corrosion (e.g., rusting) of, for example, a metalhousing surface. Such scratches and/or gouges may also act as stressconcentrators that accelerate the initiation and propagation of cracksformed in, for example, the surface of a pollution control element madeof ceramic material. Because they are relatively brittle, compared tomost metals, ceramic materials are crack sensitive. Since ceramicmonolithic pollution control elements (e.g., catalytic converterelements) are thin walled structures, the formation and propagation ofcracks can rapidly cause the ceramic element to fracture and fail whilein use. Therefore, by lowering the initial coefficient of friction ofone or both major surfaces of such a friction enhanced mounting mat,damage to the housing, the pollution control element, or both, duringthe canning process may be reduced or even prevented.

As used herein, a lower friction layer is a layer that is (a)frictionless (i.e., exhibits a very low static coefficient of frictionof about 0.15 or even lower), (b) exhibits a degree of friction that islow enough to make it easy to mount a pollution control element in ahousing with the mounting mat (i.e., exhibits a static coefficient offriction in the range of from about 0.15 up to about 0.40), or (c) atleast exhibits a static coefficient of friction that is less than thatexhibited by the friction-inducing material and that is low enough tomake it possible to mount a pollution control element in a housing withthe mounting mat. The lower friction layer can be a continuous ordiscontinuous layer.

As used herein, a portion of the friction-inducing material isconsidered covered by the lower friction layer, when that portion of thefriction-inducing material is prevented from being exposed because ofbeing (a) disposed underneath the lower friction layer, (b) embeddedinside or otherwise disposed within of the lower friction layer, or (c)both (a) and (b). In addition, the friction-inducing material isconsidered substantially covered by the lower friction layer, when thecovered friction-inducing material does not hinder, does not inhibit orat least does not prevent a corresponding pollution control element frombeing mounted in a housing using the mounting mat.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

The words “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a mounting mat that comprises“an” inorganic layer can be interpreted to mean that the mounting matincludes “one or more” inorganic layers.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements (e.g., preventingand/or treating an affliction means preventing, treating, or bothtreating and preventing further afflictions).

As used herein, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.) and any range within that range. In addition,unless expressly indicated otherwise, any numerical range recited hereinwith a lower limit and an upper limit shall include the upper and lowerlimits within the range.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In this application, guidance is providedthrough examples, which examples can be used in various combinations. Ineach instance, the recited examples serve only as a representative groupand should not be interpreted as an exclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional side view of one embodiment of a pollutioncontrol device in accordance with the present invention;

FIG. 2 is a cross-sectional side view of the mounting mat used in thepollution control device of FIG. 1; and

FIG. 3 illustrates one embodiment of a method of making a mounting matin accordance with the present invention.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

In describing preferred embodiments of the invention, specificterminology is used for the sake of clarity. The invention, however, isnot intended to be limited to the specific terms so selected, and eachterm so selected includes all technical equivalents that operatesimilarly.

Referring to FIG. 1, an exemplary pollution control device 10 accordingto the present invention comprises a housing 12, a pollution controlelement 14 mounted in the housing 12, and a mounting mat 16 disposedbetween the pollution control element 14 and the housing 12 so as tomount or otherwise secure the element 14 at a desired position withinthe housing 12. For example, a pollution control element 14 can beconsidered mounted in a housing 12, after the mat 16 is wrapped aroundthe pollution control element 14 and the resulting wrapped element isinserted and secured at a desired location within the housing (i.e.,canned). The housing 12 can include a cone-shaped inlet 13, throughwhich exhaust gasses flow into the device 10 (see arrow A), and acone-shaped outlet 15, through which the exhaust gasses flow out of thedevice 10.

Referring to FIG. 2, a mounting mat 16 according to the presentinvention can comprise one or more inorganic layers 18, afriction-inducing material 20, and a frictionless, low friction or atleast a lower friction layer 22. The at least one inorganic layer 18comprises inorganic materials suitable for mounting a pollution controlelement in a housing of a pollution control device, with the at leastone inorganic layer 18 having opposite sides or major faces 19 and 21,and each side or major face defining a major surface area. Thefriction-inducing material 20 can be in the form of a continuous ordiscontinuous layer. The friction-inducing material 20 can be bonded toor otherwise disposed on all, most or at least a substantial portion ofone or both of the major surface areas of the at least one inorganiclayer 18 so as to define a higher friction area. For example, one ormore layers of the friction-inducing material 20 may be simply deposited(e.g., sprayed or sprinkled) so as to lay on the surface of theinorganic layer(s) 18. Optionally, the friction-inducing material 20 maybe adhered to the inorganic layer(s) 18 with, for example, an organicand/or inorganic adhesive, binder and/or size. The higher friction areaexhibits a static coefficient of friction higher than that of theinorganic materials of layer(s) 18. An optional continuous ordiscontinuous bonding layer 24 can be used, when desired, to adhere thefriction-inducing material 20 to one or both sides 19 and 21 of theinorganic layer(s) 18.

The friction-inducing material 20 may be bonded or adhered to theinorganic layer(s) 18 without the need for a separate bonding layer. Inone embodiment, the bonding layer 24 may also function as the lowerfriction layer 22, for example, when the friction-inducing material 20is embedded completely, mostly or at least substantially in a matrix ofthe bonding layer 24, and the material forming the bonding layer 24exhibits the desired lower static coefficient of friction. Thefriction-inducing material 20 is considered substantially embedded, whenenough of the material 20 is not exposed that the bonding layer 24functions as the lower friction layer 22. In another embodiment, all,most or at least a substantial number of the friction-inducingparticles, whiskers, fibers or other material 20 can each be coated withan adhesive or other suitable bonding agent.

The lower friction layer 22 functions as a sacrificial layer disposed soas to cover all, most or at least a substantial portion of the higherfriction area and defines an initially exposed surface area 26 of themounting mat 16. The lower friction layer 22 covers a substantialportion of the higher friction area of the friction-inducing material20, when the exposed surface area 26 of the lower friction layer 22exhibits a lower static coefficient of friction than that of theunderlying higher friction area of the friction-inducing material 20.The bonding layer 26 may also function to completely, mostly, or atleast partially adhere all, most or at least part of the lower frictionlayer 22 to the inorganic layer(s) 18. For example, when thefriction-inducing material 20 covers only a portion of the bonding layer26 and the remaining exposed portion of the bonding layer 26 is tacky orcan become tacky (e.g., when heated), the exposed portion of the bondinglayer 26 may be available for bonding the lower friction layer 22 to theinorganic layer(s) 18. The lower friction layer 22 may also function toadhere or bond the friction-inducing material 20 to the surface of theinorganic layer(s) 18, for example, by choosing a thermoplasticpolymeric material for the lower friction layer 22 and heating the layer22 until it becomes tacky and flows so as to bond the friction-inducingmaterial 20 to the inorganic layer(s) 18. In another embodiment, acurable adhesive could be used for the lower friction layer 22, wherethe adhesive has the desired lower coefficient of friction after it iscured.

In one embodiment, a friction-inducing material 20 can be bonded to orotherwise disposed on (e.g., adhered with an organic and/or inorganicadhesive or binder, deposited so as to lay on the surface, etc.) all,most or at least a substantial portion of the major surface area of bothsides or major faces of the at least one inorganic layer 18 so as todefine a higher friction area on each side of the at least one inorganiclayer 18. Likewise, a frictionless, low friction or at least a lowerfriction layer 22 can be disposed so as to cover all, most or at least asubstantial portion of each higher friction area and define an exposedsurface area 26 on each side of the mounting mat 16, with each exposedsurface area 26 exhibiting a lower static coefficient of friction thanthat of its corresponding higher friction area lying thereunder. Thefriction-inducing material on each side of the at least one inorganiclayer 18 can be different or the same, and the lower friction layer 22covering the portion of each higher friction area can be the same ordifferent.

The exposed surface area 26 of the mounting mat 16, defined by the lowerfriction layer 22, can exhibit a relatively low static coefficient offriction, while the mounting mat 16 is used to mount a pollution controlelement 14 in a housing 12 of a pollution control device 10. Inaddition, at some time during the operation of the pollution controldevice 10, a substantial portion of the higher friction area becomesexposed and the corresponding exposed surface area of the mat 16exhibits a relatively higher static coefficient of friction. Compared tothe working lifetime of the pollution control device (e.g., 10 or moreyears), the time it takes for the higher friction area to become exposedis considerably shorter (e.g., on the order of minutes, hours or maybedays), after the pollution control device is operated.

The lower friction layer 22 is operatively adapted so as to no longercover a substantial portion of the higher friction area formed by thefriction-inducing material 20, after the mounting mat 16 has been usedto mount the pollution control element 14 in the housing 12 of thepollution control device 10. That is, after the mat 16 has been disposedbetween the pollution control element 14 and the housing 12, the lowerfriction layer 22 (a) is physically disrupted by the process of mountingthe pollution control element 14 (i.e., the canning process), (b)degrades or decomposes at the operating temperature of the pollutioncontrol device 10, or both (a) and (b), and in this way, the underlyingfriction-inducing material 20 can be exposed. In one embodiment, forexample, the lower friction layer 22 can be (a) made or otherwiseconfigured (e.g., with a thickness, a material, or both) so as to befriable, easily torn, or otherwise physically disrupted by the processof mounting the pollution control element 14 into the housing 12 of thepollution control device 10, (b) made with or otherwise comprisematerial that will substantially burn-off (e.g., an organic material),oxidize, decompose, melt, or otherwise degrade (e.g., ammoniumpentaborate) at the operating temperature of the pollution controldevice 10, or (c) both (a) and (b), and in this way, the underlyingfriction-inducing material 20 can be exposed.

In one embodiment, the lower friction layer 22 can be a layer ofpolymeric material such as, for example, high and/or low densitypolyethylene. High and low density polyethylene will completely oxidizeat temperatures of greater than or equal to about 500° C. In addition,one or both major surfaces of the mounting mats used in many commonpollution control device applications encounter surface temperatures ofabout 530° C. or even higher. Therefore, such a polyethylene lowerfriction layer will burn-off or oxidize to expose the underlyingfriction-inducing material 20, when used in many pollution controldevices.

In another embodiment, friction-inducing material 20 is in the form offriction-inducing particles and the lower friction layer 22 is in theform of one or more layers of at least one lower friction materialcoating each of the friction-inducing particles. The lower frictionmaterial for coating the particles can be chosen so as to substantiallyburn-off (e.g., an organic material), oxidize, decompose, melt, orotherwise degrade (e.g., ammonium pentaborate) at the operatingtemperature of the pollution control device 10. The lower frictionmaterial for this coating can also be chosen so as to be friable, easilytorn, or otherwise physically disrupted by the process of mounting thepollution control element 14 into the housing 12 of the pollutioncontrol device 10.

After the lower friction layer 22 no longer covers a substantial portionof the higher friction area of the friction-inducing material 20 (e.g.,after the lower friction layer 22 has been exposed to pollution controldevice operating temperatures that burn-off the lower friction layer22), the friction-inducing material 20 provides the mounting mat 16 witha high enough static coefficient of friction—between the mounting mat 16and the pollution control element 14, or the mounting mat 16 and thehousing 12, or both—to allow the pollution control element 14 to besecurely mounted (i.e., held) in place within the housing 12 at asignificantly lower mount density or mounting pressure. Reducing therequired mount density or mounting pressure of the mat 16, needed toeffectively mount the pollution control element 14 in the housing 12,can enable: (a) all, most or at least more of the inorganic mountingmaterials used in layer(s) 18 to be less resilient, less expensive, orboth (e.g., glass fibers), (b) all, most or at least less of theinorganic mounting materials used in layer(s) 18 to be more resilient,more expensive, or both (e.g., polycrystalline ceramic fibers), (c) all,most or at least more of the inorganic mounting materials used inlayer(s) 18 to be biosoluble materials (e.g., biosoluble fibers), or anycombination of (a), (b) and (c). Such biosoluble fibers can be found inpublished US patent application numbers US2009/0208385 andUS2004/0234436, which are each incorporated herein by reference in itsentirety. Being able to significantly increase the coefficient offriction on either or both major surfaces of the mounting mat 16 alsohas the potential of enabling the use of inorganic mounting materialsfor layer(s) 18 that, before now, could not be used in such mountingapplications. This invention may also allow the use of a wider varietyof mat mounting materials for any particular application than wouldnormally be possible with its use. For example, mats made of onlybiosoluble fibers or only glass fibers may be suitable for use inapplications where, before the present invention, only mats made withpolycrystalline fibers, refractory ceramic fibers, or a combination ofthese two fiber types could be used.

The lower friction layer can comprise organic material that willcompletely, mostly or at least substantially burn, decompose orotherwise degrade at the operating temperature of the pollution controldevice so as to expose all, most or at least a substantial portion ofthe higher friction area. Examples of such a lower friction layer caninclude a wide range of single and multiple layer flexible films andcoatings that are organic or substantially organic including, forexample, those made of polyethylene (e.g., high and low densitypolyethylene), polypropylene, polyester, polyvinylchloride,polyurethane, acrylic, silicone rubber, and any other suitable flexiblefilm with and without fillers.

The lower friction layer can also be dimensioned (e.g., with athickness), comprised (e.g., of a material), configured (e.g., withareas of weakness such as, for example, perforated or otherwise weakenedlines), or any combination thereof, so as to be friable, easily torn, orotherwise physically disrupted such that a portion of the higherfriction area is exposed by the process of mounting the pollutioncontrol element into the housing of the pollution control device (i.e.,the canning process).

The friction-inducing material can consist of, consist essentially of orat least comprise inorganic particles (e.g., single or multiplecomponent particles with or without a hard coating), fibers, whiskers orany combination thereof. When the friction-inducing material comprisesinorganic particles, it can be desirable for each particle to have amajor axis dimension or size in the range of from about 70 μm to about200 μm, about 50 μm to about 300 μm, about 20 μm to about 400 μm, oreven particle sizes that are smaller and/or larger. The frictioninducing material can comprises inorganic abrasive material, forexample, in the form of particles, fibers, whiskers or any combinationthereof. The friction inducing material can also comprise any suitablehard ceramic material such as, for example, at least one or acombination of alumina, silica, silicon carbide, zirconia, boronnitride, diamond, and pumice. The friction-inducing particles can bedisposed on at least one side of the inorganic layer at a concentrationlevel in the range of from about 10 g/m² to about 500 g/m².

It can be desirable for the lower friction layer to exhibit a maximumstatic coefficient of friction at room temperature (approximately 25°C.) of about 0.10, 0.15, 0.20, 0.25, or 0.30 and maybe for someapplications even a maximum static coefficient of friction at roomtemperature (approximately 25° C.) of about 0.35, 0.40, or 0.45. It canbe desirable for the friction-inducing material to exhibit a minimumstatic coefficient of friction at room temperature (approximately 25°C.) of about 0.30, 0.35, 0.40, 0.45, or 0.50, and maybe for someapplications even a minimum static coefficient of friction at roomtemperature (approximately 25° C.) of about 0.25 or even less. Thestatic coefficient of friction of the friction-inducing material at roomtemperature (approximately 25° C.) can be as high as permitted by thefriction-inducing materials chosen such as, for example, up to andincluding about 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95,1.0, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50 andmaybe even higher. Typical inorganic mat materials used to make a basemounting mat can exhibit a static coefficient of friction at roomtemperature (approximately 25° C.) in the range of from about 0.15 toabout 0.35. Whatever materials are chosen to make the present mountingmat, the lower friction layer will exhibit a lower static coefficient offriction than that exhibited by the friction-inducing material, and thefriction-inducing material will have a higher static coefficient offriction than that of the inorganic mat materials used to make the basemounting mat.

The lower friction layer can have a thickness in the range of from about1 micron up to and including about 2 mm, and preferably in the range offrom about 10 microns up to and including about 500 microns (0.5 mm) Inone embodiment of the present invention, the lower friction layer can bea high density polyethylene (HDPE) film having a thickness of about 12.7microns and the friction-inducing material can be an 80 mesh aluminagrit.

The inorganic materials can comprise, for example, inorganic fibers,intumescent material(s), or a combination of both. The at least oneinorganic layer can comprise one or more intumescent layers, one or morenon-intumescent layers, or a combination of both. For example, themounting mat can have an intumescent layer defining one side of the atleast one inorganic layer and a non-intumescent layer defining the otherside. In addition, the at least one inorganic layer can comprise anintumescent layer sandwiched or otherwise disposed between twonon-intumescent layers.

The pollution control device can exhibit a static coefficient offriction between the mounting mat and at least one or both of thepollution control element and the housing of less than or equal to about0.4, or preferably in the range of from about 0.3 to about 0.1, whilethe pollution control element is being mounted in the housing (i.e.,canned). The pollution control device can exhibit a static coefficientof friction between the mounting mat and at least one or both of thepollution control element and the housing of greater than or equal toabout 0.35, or preferably in the range of from about 0.4 to about 0.7,initially after the pollution control element is mounted in the housing(e.g., when the lower friction layer is the type that is physicallydisrupted by the canning process). After about 8 hours of beingoperated, the pollution control device can exhibit a static coefficientof friction of greater than or equal to about 0.4, or preferably in therange of from about 0.35 to about 1.0 between the mounting mat and atleast one of the pollution control element and the housing (e.g., whenthe lower friction layer is the type that burns or otherwisedisintegrates at the operating temperatures of the pollution controldevice). The operating temperature of the pollution control device canresult in the lower friction layer being subjected to a temperature inthe range of from 100° C. up to 600° C. on the housing side and fromabout 300° C. up to about 1100° C. on the side of the pollution controlelement.

The mounting mat can exhibit an initial mount density after canning ofless than or equal to about 1.2 g/cm³, or desirably in the range of fromabout 0.25 g/cm³ to about 1.05 g/cm³, or preferably in the range of fromabout 0.10 g/cm³ to about 1.0 g/cm³. The present invention may enablethe mount density of a given mounting mat to be reduced by at least 10%,15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, while still preventing themounted pollution control element from significantly moving (i.e., tothe point of contacting the housing or otherwise sustaining damage)within the housing. The mounting mat can exhibit an initial mountpressure or normal pressure after canning, at room temperature, of lessthan or equal to about 500 kPa, or desirably in the range of from about45 kPa to about 450 kPa, or preferably in the range of from about 25 kPato about 250 kPa or about 15 kPa to about 150 kPa. The present inventionmay enable the mount pressure of a given mounting mat to be reduced byat least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, while stillpreventing the mounted pollution control element from significantlymoving (i.e., to the point of contacting the housing or otherwisesustaining damage) within the housing. Because this invention can allowmounting mats to be used that exhibit lower mounting pressures and/ormount densities, a wider variety of mounting mat compositions and/ormounting mat materials can be used than would normally be possible forany particular application. As used herein, the term “mount pressure”refers to the pressure exerted by a mounting mat against a housing or apollution control element mounted within the housing by using themounting mat.

General Procedure for Making Mounting Mats

A mounting mat, according to the present invention, can be made by amethod that comprises: (a) providing at least one inorganic layercomprising inorganic materials suitable for mounting a pollution controlelement in a housing of a pollution control device, with the least oneinorganic layer having opposite sides and, and each of the oppositesides and defining a major surface area; (b) disposing afriction-inducing material on at least a portion of the major surfacearea, of at least one of the sides of the at least one inorganic layer,so as to define a higher friction area exhibiting a static coefficientof friction higher than that of the inorganic materials; and (c)disposing a lower friction layer so as to cover a portion of the higherfriction area and define an exposed surface area of the mounting mat,with the exposed surface area exhibiting a lower static coefficient offriction than that of the higher friction area. The lower friction layeris operatively adapted so as to no longer cover a substantial portion ofthe higher friction area, after the mounting mat has been used to mounta pollution control element in a housing of a pollution control device.The inorganic layer(s) can be in the form of a web or individual piecesdimensioned (e.g., by cutting, molding or other shaping technique) for adesired mounting application. The step of disposing thefriction-inducing material can comprise one or any combination ofspraying, coating, sprinkling, otherwise disposing the friction-inducingmaterial. The step of disposing the lower friction layer can compriseone or any combination of spraying, coating, laminating, or otherwisedisposing the lower friction layer.

It can be desirable for the method to further comprise disposing anoptional continuous or discontinuous bonding layer so as to adhere thefriction-inducing material onto one or both sides of the at least oneinorganic layer. The step of disposing the bonding layer can compriseone or any combination of spraying, coating or otherwise disposing thebonding layer. The bonding layer may be applied so as to at leastpartially adhere at least part of the lower friction layer to the atleast one inorganic layer.

Referring to FIG. 3, in one embodiment of a method of making a mountingmat 10 according to the present invention, a web of at least oneinorganic layer 18 is transported along a production line in adownstream direction, indicated by the arrow D, using a conventionalconveyor belt system. The web of inorganic layer(s) 18 can be madeaccording to any conventional technique (e.g., conventional wetlaid ordrylaid processes). As the inorganic layer(s) 18 moves downstream, afilm, coating or layer 24 of a bonding material or agent (e.g., a hotmelt or heat activated adhesive) is unrolled and deposited onto themajor surface on the top side 19 of the inorganic layer(s) 18. Next,friction-inducing material 20 is deposited (e.g., sprinkled, sprayed, ordropped) onto the top surface of the just applied bonding film 24. Afterthe friction-inducing material 20 is deposited onto the bonding film 24,the top side 19 of the web of inorganic layer(s) 18 is exposed to asource 30 activates the bonding agent 24, securing the friction-inducingmaterial 20 in place on the top side 19 of the inorganic layer(s) 18.Such activation of the bonding agent can occur, for example, by passingthe web through heated air (e.g., in an oven, under a heat lamp, etc.),in contact with a heated surface, under an Ultraviolet light source, orunder an e-beam source, depending on what is needed to activate thebonding agent. After the web has passed the source of activation 30, alower friction film, coating or layer 22 is laminated onto the top side19 of inorganic layer(s) 18 so as to cover the depositedfriction-inducing material 20. Optionally, the web 32 can be exposed toanother activation source 34, if desired, to cause the films 24 and 22to bond (e.g., by melting or fusing) together so as to secure the lowerfriction film 22 in place on the web 32. The resulting mounting mat web32 can be either formed (e.g., die or laser cut) into individualmounting mats 16 or wound into a roll for subsequent converting intoindividual mounting mats 16.

In an alternative embodiment of the method shown in FIG. 3, a bondingagent (e.g., a water or solvent based adhesive) can be coated (e.g.,sprayed or knife coated) so as to form a bonding layer 24 on the topside 19 of inorganic layer(s) 18. After the friction-inducing material20 is deposited onto the bonding layer 24, the top side 19 of the web ofinorganic layer(s) 18 is exposed to a source 30 that dries and/or curesthe bonding agent 24, securing the friction-inducing material 20 inplace on the side 19 of the inorganic layer(s) 18. Such drying and/orcuring of the bonding agent can occur, for example, by passing the webthrough heated air (e.g., in an oven, under a heat lamp, etc.), incontact with a heated surface, under an Ultraviolet light source, orunder an e-beam source, depending on the bonding agent used. After theweb has passed the source 30, a layer 22 of lower friction material iscoated (e.g., sprayed or knife coated) so as to cover the depositedfriction-inducing material 20. Optionally, the web 32 can be exposed toanother activation source 34, if desired, to dry and/or cure the lowerfriction layer 22 and, thereby, bond the layers 24 and 22 together so asto secure the lower friction layer 22 in place on the web 32.

The following Examples have been selected merely to further illustratefeatures, advantages, and other details of various embodiments of thepresent invention. It is to be expressly understood, however, that whilethe Examples serve this purpose, the particular details are not to beconstrued in a manner that would unduly limit the scope of thisinvention.

TEST METHODS Static Coefficient of Friction

The static coefficient of friction value is calculated from the amountof force needed to initially move two 1.75 inch by 1.75 inch squaremounting mat test samples across a 409 stainless steel test surface,while the samples are under a selected normal pressure. The staticcoefficient of friction is defined as the peak force needed to cause thesample to initially begin sliding on the test surface divided by thearea of the samples.

The equipment used to determine the static coefficient of friction ofthe test samples includes a center heated metal platen that is attachedto a load frame and disposed between two outer heated metal platens. Oneouter platen is fixtured with an air cylinder capable of applying up to10 pounds per square inch (psi) of pressure between the platens. One 409stainless steel metal plate (approximately 2.15 inches wide, 2.24 incheslong and 0.57 inches thick) is set into a shallow vertical slotapproximately 0.57 inches deep set into each side of the center heatedplaten. A similar slot is formed in the interior facing side of each ofthe two outer metal platens. One inconel metal plate (approximately 2.15inches wide, 2.24 inches long and 0.12 inches thick) is set into theslot of each outer platen. Four 0.4 inch by 0.4 inch deep groovespositioned ninety degrees to the moving direction of the load frame areformed on the exposed surface of each inconel metal plate. One mountingmat test sample is placed between each of the two 409 stainless steelmetal plates and one corresponding inconel metal plate.

The load frame is attached to a load cell capable of measuring the forceand displacement of the center platen. Both outer platens are set infixtures capable being adjusted such that the two mat samples placedagainst the 409 stainless steel plates may be centered below the loadframe. The load frame pulls the center platen vertically at a rate of 4inches per minute during the test while the outer platens arestationary. Sufficient insulation and/or cooling is provided between theload cell and the heated center platen to prevent overheating of theload cell during testing. All samples are first heated to the testtemperature and allowed to soak for 10 minutes before testing unlessotherwise indicated.

Each grooved inconel metal plate is designed to prevent slippage betweenthe corresponding outer metal platen and mat test sample. Each 409stainless steel plate simulates the surface of a pollution controldevice housing. These stainless steel plates can be replaced withalternative plates made with other materials to simulate the surface ofany other housing or pollution control element.

EXAMPLES Bond Coat Composition A

600 grams of Grace #5 expanded vermiculite (W.R. Grace, Cambridge Mass.)and 2000 milliliters of water are placed in a Waring Commercial HeavyDuty Blender (model 37BL84 (CB6)) and mixed at low speed for a total ofsix minutes with three separate two minute cycles to produce a slurry.50 parts by weight of this slurry is mixed with 10 parts by weight Nalco2327 (Nalco Company, Naperville, Ill.) colloidal silica and 10 parts byweight 600BP latex (Wacker Chemie AG, Stuttgart, Germany).

Bond Coat Composition B

50 parts by weight of vermiculite slurry from Bond Coat Composition A ismixed with 50 parts by weight Nalco 2327, 30 parts by weight Dixie Clay(R. T. Vanderbilt Company, Inc., Norwalk, Conn.), and 5 parts by weight600BP latex.

Coefficient of Friction Examples Comparative Examples 1 and 2

1.75 inch by 1.75 inch square samples of 1600 grams per square meter of3M™ Interam™ 800 Mounting mat were cut from sheets for testing.

Comparative Examples 3 and 4

Bond Coat Composition A was brushed onto 1.75 by 1.75 inch squaresamples of 1600 grams per square meter 3M™ Interam™ 800 mounting mat ata coating weight of 183 grams per square meter and “Duralum” G52 BrownAluminum Oxide Grade 80 (Washington Mills Electro Minerals Corp.,Niagara Falls, N.Y.) was sprinkled over the wet bond coat at a coatingweight of 230 grams per square meter. The sample was dried beforetesting.

Examples 5 and 6

Dried samples prepared as in Comparative Examples 3 and 4 were lightlysprayed with 3M Super 77 adhesive (3M, St. Paul, Minn.) and covered with0.75 mil thick High Density Polyethylene Film (Hilex Poly Company, LLC,Hartsville, S.C.).

Examples 7 and 8

Samples were prepared as in Examples 5 and 6 using 1200 gram per squaremeter MLS-2 blanket (Mitsubishi Plastic Composites America, Inc.,Chesapeake, Va.). 954 grams per square meter Bond Coat Composition B wasbrushed on the sample and 387 grams per square meter “Duralum” G52 BrownAluminum Oxide Grade P150 (Washington Mills Electro Minerals Corp.,Niagara Falls, N.Y.) was sprinkled on the sample and the sample dried.The dried samples were lightly sprayed with 3M Super 77 adhesive (3M,St. Paul, Minn.) and covered with 0.5 mil thick High DensityPolyethylene Film (Hilex Poly Company, LLC, Hartsville, S.C.).

TABLE 1 Static Coefficient Example Test Condition of Friction 1 25degrees Centigrade 0.31 2 200 degrees Centigrade 0.38 3 25 degreesCentigrade 0.51 4 200 degrees Centigrade 0.57 5 25 degrees Centigrade0.25 6 200 degrees Centigrade 0.54 7 25 degrees Centigrade 0.18 8 Soakedfor one hour at 500 0.45 degrees Centigrade then tested at 25 degreesCentigrade

A comparison of the above tabulated data for Examples 5 and 7 with thatof Examples 6 and 8, respectively, reveals how dramatically the staticcoefficient of friction can change between the mounting mat and thehousing, the mounting mat and the pollution control element, or both, byusing the present invention. A comparison of Examples 6 and 8 alsoindicates how the size of friction-inducing particles can impact thestatic coefficient of friction. Example 6 used larger friction-inducingparticles (Grade 80) and obtain a higher static coefficient of friction,while Example 8 used smaller friction-inducing particles (Grade 150) andobtain a lower static coefficient of friction.

Various Embodiments Mounting Mat Embodiments

1. A mounting mat for mounting a pollution control element in a housingof a pollution control device, the mounting mat comprising:

-   -   at least one inorganic layer (e.g., in the form of a web, sheet        or mat) comprising inorganic materials suitable for mounting a        pollution control element in a housing of a pollution control        device, with the at least one inorganic layer having opposite        sides, and each the side defining a major surface area;    -   a friction-inducing material disposed on at least a portion of        the major surface area, of at least one of the sides of the at        least one inorganic layer, so as to define a higher friction        area exhibiting a static coefficient of friction higher than        that of the inorganic materials forming the major surface area;        and    -   a lower friction layer disposed so as to cover at least a        portion of the higher friction area and define an exposed        surface area of the mounting mat, with the exposed surface area        exhibiting a lower static coefficient of friction than that of        the higher friction area,    -   wherein the lower friction layer is operatively adapted so as to        no longer cover a substantial portion of the higher friction        area, after the mounting mat has been used to mount a pollution        control element in a housing of a pollution control device.

2. The mounting mat according to embodiment 1, wherein the lowerfriction layer comprises organic material that will degrade at theoperating temperature of the pollution control device so as to expose aportion of the higher friction area.

3. The mounting mat according to embodiment 1 or 2, wherein the lowerfriction layer comprises organic material that will burn at theoperating temperature of the pollution control device so as to expose aportion of the higher friction area.

4. The mounting mat according to embodiment 1 or 2, wherein the lowerfriction layer is dimensioned, comprised, configured, or any combinationthereof, so as to be physically disrupted such that a portion of thehigher friction area is exposed by the process of mounting the pollutioncontrol element into the housing of the pollution control device.

5. The mounting mat according to any one of embodiments 1 to 4, whereinthe exposed surface area of the mounting mat defined by the lowerfriction layer exhibits a relatively low static coefficient of friction,while the mounting mat is used to mount a pollution control element in ahousing of a pollution control device, and at some time during theoperation of the pollution control device, the substantial portion ofthe higher friction area becomes exposed and exhibits a relativelyhigher static coefficient of friction.

6. The mounting mat according to any one of embodiments 1 to 5, whereinthe inorganic materials comprise inorganic fibers, intumescentmaterials, or a combination of both.

7. The mounting mat according to any one of embodiments 1 to 6, whereinthe at least one inorganic layer comprises an intumescent layer and anon-intumescent layer.

8. The mounting mat according to any one of embodiments 1 to 7, whereina friction-inducing material is disposed on at least a portion of themajor surface area of both sides of the at least one inorganic layer soas to define a higher friction area on each side of the at least oneinorganic layer, and a lower friction layer is disposed so as to cover aportion of each the higher friction area and define an exposed surfacearea on each side of the mounting mat, with each the exposed surfacearea exhibiting a lower static coefficient of friction than that of itscorresponding higher friction area.

9. The mounting mat according to embodiment 8, wherein thefriction-inducing material on each side of the at least one inorganiclayer is different or the same, and the lower friction layer covering aportion of each the higher friction area is the same or different.

10. The mounting mat according to any one of embodiments 1 to 9, whereinthe friction-inducing material comprises inorganic particles, fibers,whiskers or any combination thereof.

11. The mounting mat according to embodiment 10, wherein thefriction-inducing material comprises inorganic particles, with eachparticle having a major axis dimension in the range of from about 70 μmto about 200 μm.

12. The mounting mat according to embodiment 10 or 11, wherein thefriction-inducing material comprises inorganic fibers, with eachinorganic fiber having a major axis dimension in the range of from about50 μm to about 300 μm.

13. The mounting mat according to any one of embodiments 10 to 12,wherein the friction-inducing material comprises inorganic whiskers,with each inorganic whisker having a major axis dimension in the rangeof from about 20 μm to about 400 μm.

14. The mounting mat according to any one of embodiments 1 to 13,wherein the friction inducing material comprises inorganic abrasivematerial.

15. The mounting mat according to any one of embodiments 1 to 14,wherein the friction inducing material comprises at least one or acombination of alumina, silica, silicon carbide, zirconia, boronnitride, diamond, and pumice.

16. The mounting mat according to any one of embodiments 1 to 15,wherein the friction-inducing material comprises particles disposed onat least one side of the inorganic layer at a concentration level in therange of from about 10 g/m² to about 500 g/m².

17. The mounting mat according to any one of embodiments 1 to 16,wherein the lower friction layer exhibits a maximum static coefficientof friction of about 0.35.

18. The mounting mat according to any one of embodiments 1 to 17,wherein the friction-inducing material exhibits a minimum staticcoefficient of friction of about 0.25.

19. The mounting mat according to any one of embodiments 1 to 18,further comprising a bonding layer disposed so as to adhere thefriction-inducing material on at least the portion of the major surfacearea of at least one of the sides of the at least one inorganic layer.

20. The mounting mat according to embodiment 19, wherein the bondinglayer at least partially adheres at least part of the lower frictionlayer to the at least one inorganic layer so as to cover at least aportion of the higher friction area.

Pollution Control Device Embodiments

21. A pollution control device comprising:

-   -   a housing;    -   a pollution control element mounted in the housing; and    -   a mounting mat according to any one of embodiments 1 to 20,    -   wherein the mounting mat is disposed between the pollution        control element and the housing.

22. The pollution control device of embodiment 21, wherein the pollutioncontrol device exhibits a static coefficient of friction between themounting mat and at least one of the pollution control element and thehousing of less than or equal to about 0.4, while the pollution controlelement is being mounted in the housing.

23. The pollution control device of embodiment 21, wherein the pollutioncontrol device exhibits a static coefficient of friction between themounting mat and at least one of the pollution control element and thehousing of greater than or equal to about 0.35, initially after thepollution control element is mounted in the housing.

24. The pollution control device of any one of embodiments 21 to 23,wherein after 8 hours of being operated, the pollution control deviceexhibits a static coefficient of friction of greater than or equal toabout 0.4, between the mounting mat and at least one of the pollutioncontrol element and the housing.

25. The pollution control device of any one of embodiments 21 to 24,wherein the mounting mat exhibits a mount density of less than or equalto about 1.2 g/cm³.

26. The pollution control device of any one of embodiments 21 to 25,wherein the mounting mat exhibits a mount pressure of less than or equalto about 500 kPa at room temperature.

Method Embodiments

27. A method of making a mounting mat for mounting a pollution controlelement in a housing of a pollution control device, the methodcomprising:

-   -   providing at least one inorganic layer comprising inorganic        materials suitable for mounting a pollution control element in a        housing of a pollution control device, with the at least one        inorganic layer having opposite sides, and each of the opposite        sides defining a major surface area;    -   disposing a friction-inducing material on at least a portion of        the major surface area, of at least one of the sides of the at        least one inorganic layer, so as to define a higher friction        area exhibiting a static coefficient of friction higher than        that of the inorganic materials; and    -   disposing a lower friction layer so as to cover a portion of the        higher friction area and define an exposed surface area of the        mounting mat, with the exposed surface area exhibiting a lower        static coefficient of friction than that of the higher friction        area,    -   wherein the lower friction layer is operatively adapted so as to        no longer cover a substantial portion of the higher friction        area, after the mounting mat has been used to mount a pollution        control element in a housing of a pollution control device.

This invention may take on various modifications and alterations withoutdeparting from its spirit and scope. Accordingly, this invention is notlimited to the above-described but is to be controlled by thelimitations set forth in the following claims and any equivalentsthereof. This invention may be suitably practiced in the absence of anyelement not specifically disclosed herein. All patents and patentapplications cited above, including those in the Background section, areincorporated by reference into this document in total.

1. A mounting mat for mounting a pollution control element in a housing of a pollution control device, said mounting mat comprising: at least one inorganic layer comprising inorganic fibers, and optionally other inorganic materials, suitable for mounting a pollution control element in a housing of a pollution control device, with said at least one inorganic layer having opposite sides, and each said side defining a major surface area; a friction-inducing inorganic material disposed on at least a portion of the major surface area, of at least one of the sides of said at least one inorganic layer, so as to define a higher friction area exhibiting a static coefficient of friction higher than that of said inorganic materials; and a lower friction layer comprising organic material disposed so as to cover at least a portion of said higher friction area and define an exposed surface area of said mounting mat, with said exposed surface area exhibiting a lower static coefficient of friction than that of said higher friction area, wherein said lower friction layer is operatively adapted so as to no longer cover a substantial portion of said higher friction area, after said mounting mat has been used to mount a pollution control element in a housing of a pollution control device.
 2. The mounting mat according to claim 1, wherein said lower friction layer at least one of (a) comprises organic material that will degrade at the operating temperature of the pollution control device so as to expose a portion of said higher friction area, (b) comprises organic material that will burn at the operating temperature of the pollution control device so as to expose a portion of said higher friction area, (c) is dimensioned, comprised, configured, or any combination thereof, so as to be physically disrupted such that a portion of said higher friction area is exposed by the process of mounting the pollution control element into the housing of the pollution control device, or (d) any combination of (a), (b) and (c).
 3. The mounting mat according to claim 1, wherein the exposed surface area of said mounting mat defined by said lower friction layer exhibits a relatively low static coefficient of friction compared to that of the higher friction area, while said mounting mat is used to mount a pollution control element in a housing of a pollution control device, and at some time during the operation of the pollution control device, the substantial portion of said higher friction area becomes exposed and exhibits a relatively higher static coefficient of friction compared to that of said lower friction layer.
 4. The mounting mat according to claim 1, wherein a friction-inducing inorganic material is disposed on at least a portion of the major surface area of both sides of said at least one inorganic layer so as to define a higher friction area on each side of said at least one inorganic layer, and a lower friction layer is disposed so as to cover a portion of each said higher friction area and define an exposed surface area on each side of said mounting mat, with each said exposed surface area exhibiting a lower static coefficient of friction than that of its corresponding higher friction area.
 5. The mounting mat according to claim 1, wherein said friction-inducing inorganic material comprises (a) inorganic particles, with each particle having a major axis dimension in the range of from about 70 μm to about 200 μm, (b) inorganic fibers, with each inorganic fiber having a major axis dimension in the range of from about 50 μm to about 300 μm, (c) inorganic whiskers, with each inorganic whisker having a major axis dimension in the range of from about 20 μm to about 400 μm, or (d) any combination of (a), (b) and (c).
 6. The mounting mat according to claim 1, wherein said friction inducing material comprises inorganic abrasive material.
 7. The mounting mat according to claim 1, wherein said friction-inducing inorganic material comprises particles disposed on at least one side of said inorganic layer at a concentration level in the range of from about 10 g/m² to about 500 g/m².
 8. The mounting mat according to claim 1, wherein said lower friction layer exhibits a maximum static coefficient of friction of about 0.35.
 9. The mounting mat according to claim 1, wherein said friction-inducing inorganic material exhibits a minimum static coefficient of friction of about 0.25.
 10. The mounting mat according to claim 1, further comprising a bonding layer disposed so as to adhere said friction-inducing inorganic material on at least the portion of the major surface area of at least one of the sides of said at least one inorganic layer.
 11. The mounting mat according to claim 10, wherein said bonding layer at least partially adheres at least part of said lower friction layer to said at least one inorganic layer so as to cover at least a portion of said higher friction area.
 12. A pollution control device comprising: a housing; a pollution control element mounted in said housing; and a mounting mat according to claim 1, wherein said mounting mat is disposed between said pollution control element and said housing.
 13. The pollution control device of claim 12, wherein said pollution control device exhibits a static coefficient of friction between said mounting mat and at least one of said pollution control element and said housing of less than or equal to about 0.4, while said pollution control element is being mounted in said housing.
 14. The pollution control device of claim 12, wherein said pollution control device exhibits a static coefficient of friction between said mounting mat and at least one of said pollution control element and said housing of less than about 0.35, while said pollution control element is being mounted in said housing, and said pollution control device exhibits a static coefficient of friction between said mounting mat and at least one of said pollution control element and said housing of greater than or equal to about 0.35, initially after said pollution control element is mounted in said housing.
 15. The pollution control device of claim 12 to 14, wherein after 8 hours of being operated, said pollution control device exhibits a static coefficient of friction of greater than or equal to about 0.4, between said mounting mat and at least one of said pollution control element and said housing.
 16. The pollution control device of claim 12, wherein said mounting mat exhibits (a) a mount density of less than or equal to about 1.2 g/cm³, (b) a mount pressure of less than or equal to about 500 kPa at room temperature, or (c) both (a) and (b).
 17. A method of making a mounting mat for mounting a pollution control element in a housing of a pollution control device, said method comprising: providing at least one inorganic layer comprising inorganic materials suitable for mounting a pollution control element in a housing of a pollution control device, with the at least one inorganic layer having opposite sides, and each of the opposite sides defining a major surface area; disposing a friction-inducing inorganic material on at least a portion of the major surface area, of at least one of the sides of the at least one inorganic layer, so as to define a higher friction area exhibiting a static coefficient of friction higher than that of the inorganic materials; and disposing a lower friction layer so as to cover a portion of the higher friction area and define an exposed surface area of the mounting mat, with the exposed surface area exhibiting a lower static coefficient of friction than that of said higher friction area, wherein the lower friction layer is operatively adapted so as to no longer cover a substantial portion of the higher friction area, after the mounting mat has been used to mount a pollution control element in a housing of a pollution control device.
 18. The mounting mat according to claim 2, wherein said friction-inducing inorganic material comprises (a) inorganic particles, with each particle having a major axis dimension in the range of from about 70 μm to about 200 μm, (b) inorganic fibers, with each inorganic fiber having a major axis dimension in the range of from about 50 μm to about 300 μm, (c) inorganic whiskers, with each inorganic whisker having a major axis dimension in the range of from about 20 μm to about 400 μm, or (d) any combination of (a), (b) and (c).
 19. The pollution control device of claim 12, wherein said lower friction layer at least one of (a) comprises organic material that will degrade at the operating temperature of the pollution control device so as to expose a portion of said higher friction area, (b) comprises organic material that will burn at the operating temperature of the pollution control device so as to expose a portion of said higher friction area, (c) is dimensioned, comprised, configured, or any combination thereof, so as to be physically disrupted such that a portion of said higher friction area is exposed by the process of mounting the pollution control element into the housing of the pollution control device, or (d) any combination of (a), (b) and (c).
 20. The pollution control device of claim 12, wherein the exposed surface area of said mounting mat defined by said lower friction layer exhibits a relatively low static coefficient of friction compared to that of the higher friction area, and at some time during the operation of said pollution control device, the substantial portion of said higher friction area becomes exposed and exhibits a relatively higher static coefficient of friction compared to that of said lower friction layer. 